The type of immune response generated to infection or other antigenic challenge can generally be distinguished by the subset of T helper (Th) cells involved in the response. The Th1 subset is responsible for classical cell-mediated functions such as delayed-type hypersensitivity and activation of cytotoxic T lymphocytes (CTLs), whereas the Th2 subset functions more effectively as a helper for B-cell activation. The type of immune response to an antigen is generally influenced by the cytokines produced by the cells responding to the antigen. Differences in the cytokines secreted by Th1 and Th2 cells are believed to reflect different biological functions of these two subsets. See, for example, Romagnani (2000) Ann. Allergy Asthma Immunol. 85:9-18.
The Th1 subset may be particularly suited to respond to viral infections, intracellular pathogens, and tumor cells because it secretes IL-2 and IFN-γ, which activate CTLs. The Th2 subset may be more suited to respond to free-living bacteria and helminthic parasites and may mediate allergic reactions, since IL-4 and IL-5 are known to induce IgE production and eosinophil activation, respectively. In general, Th1 and Th2 cells secrete distinct patterns of cytokines and so one type of response can moderate the activity of the other type of response. A shift in the Th1/Th2 balance can result in an allergic response, for example, or, alternatively, in an increased CTL response.
For many infectious diseases, such as tuberculosis and malaria, Th2-type responses are of little protective value against infection. Proposed vaccines using small peptides derived from the target antigen and other currently used antigenic agents that avoid use of potentially infective intact viral particles, do not always elicit the immune response necessary to achieve a therapeutic effect. The lack of a therapeutically effective human immunodeficiency virus (HIV) vaccine is an unfortunate example of this failure. Protein-based vaccines typically induce Th2-type immune responses, characterized by high titers of neutralizing antibodies but without significant cell-mediated immunity.
Moreover, some types of antibody responses are inappropriate in certain indications, most notably in allergy where an IgE antibody response can result in anaphylactic shock. Generally, allergic responses also involve Th2-type immune responses. Allergic responses, including those of allergic asthma, are characterized by an early phase response, which occurs within seconds to minutes of allergen exposure and is characterized by cellular degranulation, and a late phase response, which occurs 4 to 24 hours later and is characterized by infiltration of eosinophils into the site of allergen exposure. Specifically, during the early phase of the allergic response, allergen cross-links IgE antibodies on basophils and mast cells, which in turn triggers degranulation and the subsequent release of histamine and other mediators of inflammation from mast cells and basophils. During the late phase response, eosinophils infiltrate into the site of allergen exposure (where tissue damage and dysfunction result).
Antigen immunotherapy for allergic disorders involves the subcutaneous injection of small, but gradually increasing amounts, of antigen. Such immunization treatments present the risk of inducing IgE-mediated anaphylaxis and do not efficiently address the cytokine-mediated events of the allergic late phase response. Thus far, this approach has yielded only limited success.
Administration of certain DNA sequences, generally known as immunostimulatory sequences or “ISS,” induces an immune response with a Th1-type bias as indicated by secretion of Th1-associated cytokines. Administration of an immunostimulatory polynucleotide with an antigen results in a Th1-type immune response to the administered antigen. Roman et al. (1997) Nature Med. 3:849-854. For example, mice injected intradermally with Escherichia coli (E. coli) β-galactosidase (β-Gal) in saline or in the adjuvant alum responded by producing specific IgG1 and IgE antibodies, and CD4+ cells that secreted IL-4 and IL-5, but not IFN-γ, demonstrating that the T cells were predominantly of the Th2 subset. However, mice injected intradermally (or with a tyne skin scratch applicator) with plasmid DNA (in saline) encoding β-Gal and containing an ISS responded by producing IgG2a antibodies and CD4+ cells that secreted IFN-γ, but not IL-4 and IL-5, demonstrating that the T cells were predominantly of the Th1 subset. Moreover, specific IgE production by the plasmid DNA-injected mice was reduced 66-75%. Raz et al. (1996) Proc. Natl. Acad. Sci. USA 93:5141-5145. In general, the response to naked DNA immunization is characterized by production of IL-2, TNFα and IFN-γ by antigen-stimulated CD4+ T cells, which is indicative of a Th1-type response. This is particularly important in treatment of allergy and asthma as shown by the decreased IgE production. The ability of immunostimulatory polynucleotides to stimulate a Th1-type immune response has been demonstrated with bacterial antigens, viral antigens and with allergens (see, for example, WO 98/55495).
Other references describing ISS include: Krieg et al. (1989) J. Immunol. 143:2448-2451; Tokunaga et al. (1992) Microbiol. Immunol. 36:55-66; Kataoka et al. (1992) Jpn. J. Cancer Res. 83:244-247; Yamamoto et al. (1992) J. Immunol. 148:4072-4076; Mojcik et al. (1993) Clin. Immuno. and Immunopathol. 67:130-136; Branda et al. (1993) Biochem. Pharmacol. 45:2037-2043; Pisetsky et al. (1994) Life Sci. 54(2):101-107; Yamamoto et al. (1994a) Antisense Research and Development. 4:119-122; Yamamoto et al. (1994b) Jpn. J. Cancer Res. 85:775-779; Raz et al. (1994) Proc. Natl. Acad. Sci. USA 91:9519-9523; Kimura et al. (1994) J. Biochem. (Tokyo) 116:991-994; Krieg et al. (1995) Nature 374:546-549; Pisetsky et al. (1995) Ann. N.Y. Acad. Sci. 772:152-163; Pisetsky (1996a) J. Immunol. 156:421-423; Pisetsky (1996b) Immunity 5:303-310; Zhao et al. (1996) Biochem. Pharmacol. 51:173-182; Yi et al. (1996) J. Immunol. 156:558-564; Krieg (1996) Trends Microbiol. 4(2):73-76; Krieg et al. (1996) Antisense Nucleic Acid Drug Dev. 6:133-139; Klinman et al. (1996) Proc. Natl. Acad. Sci. USA. 93:2879-2883; Raz et al. (1996); Sato et al. (1996) Science 273:352-354; Stacey et al. (1996) J. Immunol. 157:2116-2122; Ballas et al. (1996) J. Immunol. 157:1840-1845; Branda et al. (1996) J. Lab. Clin. Med. 128:329-338; Sonehara et al. (1996) J. Interferon and Cytokine Res. 16:799-803; Klinman et al. (1997) J. Immunol. 158:3635-3639; Sparwasser et al. (1997) Eur. J. Immunol. 27:1671-1679; Roman et al. (1997); Carson et al. (1997) J. Exp. Med. 186:1621-1622; Chace et al. (1997) Clin. Immunol. and Immunopathol. 84:185-193; Chu et al. (1997) J. Exp. Med. 186:1623-1631; Lipford et al. (1997a) Eur. J. Immunol. 27:2340-2344; Lipford et al. (1997b) Eur. J. Immunol. 27:3420-3426; Weiner et al. (1997) Proc. Natl. Acad. Sci. USA 94:10833-10837; Macfarlane et al. (1997) Immunology 91:586-593; Schwartz et al. (1997) J. Clin. Invest. 100:68-73; Stein et al. (1997) Antisense Technology, Ch. 11 pp. 241-264, C. Lichtenstein and W. Nellen, Eds., IRL Press; Wooldridge et al. (1997) Blood 89:2994-2998; Leclerc et al. (1997) Cell. Immunol. 179:97-106; Kline et al. (1997) J. Invest. Med. 45(3):282A; Yi et al. (1998a) J. Immunol. 160:1240-1245; Yi et al. (1998b) J. Immunol. 160:4755-4761; Yi et al. (1998c) J. Immunol. 160:5898-5906; Yi et al. (1998d) J. Immunol. 161:4493-4497; Krieg (1998) Applied Antisense Oligonucleotide Technology Ch. 24, pp. 431-448, C. A. Stein and A. M. Krieg, Eds., Wiley-Liss, Inc.; Krieg et al. (1998a) Trends Microbiol. 6:23-27; Krieg et al. (1998b) J. Immunol. 161:2428-2434; Krieg et al. (1998c) Proc. Natl. Acad. Sci. USA 95:12631-12636; Spiegelberg et al. (1998) Allergy 53(45S):93-97; Horner et al. (1998) Cell Immunol. 190:77-82; Jakob et al. (1998) J. Immunol. 161:3042-3049; Redford et al. (1998) J. Immunol. 161:3930-3935; Weeratna et al. (1998) Antisense & Nucleic Acid Drug Development 8:351-356; McCluskie et al. (1998) J. Immunol. 161(9):4463-4466; Gramzinski et al. (1998) Mol. Med. 4:109-118; Liu et al. (1998) Blood 92:3730-3736; Moldoveanu et al. (1998) Vaccine 16: 1216-1224; Brazolot Milan et al. (1998) Proc. Natl. Acad. Sci. USA 95:15553-15558; Briode et al. (1998) J. Immunol. 161:7054-7062; Briode et al. (1999) Int. Arch. Allergy Immunol. 118:453-456; Kovarik et al. (1999) J. Immunol. 162:1611-1617; Spiegelberg et al. (1999) Pediatr. Pulmonol. Suppl. 18:118-121; Martin-Orozco et al. (1999) Int. Immunol. 11:1111-1118; EP 468,520; WO 96/02555; WO 97/28259; WO 98/16247; WO 98/18810; WO 98/37919; WO 98/40100; WO 98/52581; WO 98/55495; WO 98/55609 and WO 99/11275. See also Elkins et al. (1999) J. Immunol. 162:2291-2298, WO 98/52962, WO 99/33488, WO 99/33868, WO 99/51259 and WO 99/62923. See also Zimmermann et al. (1998) J. Immunol. 160:3627-3630; Krieg (1999) Trends Microbiol. 7:64-65 and U.S. Pat. Nos. 5,663,153, 5,723,335 and 5,849,719. See also Liang et al. (1996) J. Clin. Invest. 98:1119-1129; Bohle et al. (1999) Eur. J. Immunol. 29:2344-2353 and WO 99/56755. See also WO 99/61056; WO 00/06588; WO 00/16804; WO 00/21556; WO 00/54803; WO 00/61151; WO 00/67023; WO 00/67787 and U.S. Pat. No. 6,090,791. See also Manzel et al. (1999) Antisense Nucl. Acid Drug Dev. 9:459-464; Verthelyi et al. (2001) J. Immunol. 166:2372-2377; WO 01/15726; WO 01/12223; WO 01/22972; WO 01/22990; WO 01/35991; WO 01/51500; WO 01/54720; U.S. Pat. Nos. 6,174,872, 6,194,388, 6,207,646, 6,214,806, 6,218,371, 6,239,116.
ISS generally include a CG sequence. Nucleotides flanking the CG of an ISS also appear to play a role in the immunomodulatory activity of the polynucleotide. There remains a need for continued identification of ISS for use in immunomodulatory polynucleotides.
All patents, patent applications, and publications cited herein are hereby incorporated by reference in their entirety.